Note 6 - Employee Benefit Plans - Change in Benefit Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan [Abstract]
Benefit obligation at beginning of year	$ 149,426	$ 148,143
Service cost	3,659	3,794	$ 6,262
Interest cost	8,302	7,974	5,476
Change due to mortality change	2,430	643
Change due to discount rate change	10,819	(3,635)
Actuarial return	1,714	401
Benefits paid	(8,346)	(7,894)
Benefit obligation at end of year	168,004	149,426	148,143
Fair value of plan assets at beginning of year	176,958	175,159
Actual return on plan assets	15,722	7,937
Employer contributions	0	1,756
Benefits paid	(8,346)	(7,894)
Fair value of plan assets at end of year	184,334	176,958	$ 175,159
Funded status at end of year	$ 16,330	$ 27,532